I have been reading several posts about Lean and Six Sigma. The way the two philosophies apparently differentiate is that Lean is all about eliminating waste, and Six Sigma is all about eliminating variation. As with many concepts in Eastern philosophy, things appear simple at first sight, and as we learn more about it, the concept gets deeper and deeper. In today’s post, I will look at the Toyota Production System in the light of “waste”.
The Japanese word for waste is “muda”. Muda literally means no value. Mu = no or lack of, and da = value. The idea that Toyota Production System is based on the principle of eliminating waste was put forth by Taiichi Ohno, the father of Toyota Production System. Ohno identified seven types of wastes as follows;
- Waste of overproduction
- Waste of time on hand (waiting)
- Waste in transportation
- Waste of processing itself
- Waste of stock on hand (inventory)
- Waste of movement
- Waste of making defective products.
A close review of these wastes shows that many of these wastes are interconnected. If you have inventory, you will also have transportation. Waste of processing can also lead to waste of movement. Waste of overproduction is sometimes called as the mother of all wastes since it can lead to all of the other types of wastes. Several practitioners have identified more types of wastes, of which the most popular is the “under utilization of human talent”.
Let’s Go Deeper:
I do not agree with the generalization that lean is about eliminating waste. Toyota speaks about 3 “Mu”s. They are as follows;
- Muda = waste
- Muri = overburden
- Mura = unevenness
Things get complicated when we learn that Toyota uses Muda in 3 different meanings. The Japanese language has several writing systems. Muda has roots in Chinese language. Japanese can write Muda in 3 different writing styles to add particular nuances.
Muda in kanji (based on Chinese scripts) means waste that was created by existing management policies. Muda in hiragana (based on native or naturalized Japanese words) means waste that cannot be eliminated right now. Muda in katakana (based on foreign words or words used with emphasis) means waste that can be eliminated immediately. (Source: Kaizen Express, Toshiko Narusawa and John Shook)
Taiichi Ohno defined the Toyota Production System as follows;
“The fundamental doctrine of Toyota Production System is the total elimination of waste”.
Muri literally means “unreasonable” in Japanese. Mu = No or lack of, and Ri = reason. Both muda and muri can be explained in Japanese as a “lack of something” or as “no + something”. Muri also has several nuanced meanings in Japanese. “Muri suru” in Japanese means “to take things too far” or “to overdo”. In TPS, muri refers to overburdening the operator so that it can result in injuries or defective products. This is akin to saying work harder to produce more products while not improving the process. The standard work is often used as a means to tackle muri.
Mura is defined as “uneven”. I have not seen mura explained as a “lack of evenness” (Mu + evenness) in Japanese. For example, the unevenness is in how we manufacture products. We should produce products so that we can meet the customers’ demands. From a producer’s standpoint, producing product of one type makes the most sense since it maximizes efficiency. This is akin to the famous Ford quote “as long as it is black”. However, each customer is unique. He may want “red” instead of black. He may want a different model than what you want to make. The unevenness is in how the units are being produced without keeping the end picture in mind. TPS utilizes both kanban and heijunka to level production.
Taiichi Ohno defined the Toyota Production System in light of this as follows;
“The goal of the Toyota Production System is to level the flows or production and goods.”
The 3 Mu’s:
The keen learner can see that muda, muri and mura are closely intertwined. Toyota has even defined muri and mura as two forms of muda!
“Both mura and muri are thought of as types of muda, or waste, and should be eliminated.”
Mikio Kitano, former President of Toyota Motor Manufacturing of North America Inc, has identified the order to approach the 3 Mu’s for a new process. (Muri -> Mura -> Muda)
“First, Muri focuses on the preparation and planning of the process, or what can be avoided proactively. And, then, Mura focuses on implementation and the elimination of fluctuation at the operations level, such as quality and volume. The third — Muda — is discovered after the process is in place and is dealt with reactively. It is seen by variation in output. It is the role of Management to examine the Muda, or waste, in the processes and eliminate the deeper causes by considering the connections to Muri and Mura of the system. The Muda – waste – and Mura – inconsistencies – must be fed back to the Muri, or planning, stage for the next project.
The continuous cycle of self-examination allows for the outcomes to continuously improve. This brings in Management’s responsibility:
- to provide and improve a flexible system, and
- to connect the workforce and the customer.”
As I have already stated, I do not believe in the generalization that TPS or Lean is about the elimination of waste. This makes it a tool based system. TPS is a holistic management system. Once we look deeper at how the “waste” is viewed, we understand that this does not mean just seven types of waste.
There is a counter-intuitive aspect to muri. Taiichi Ohno was famous for asking to produce the same amount of products by utilizing fewer employees. He would say to remove one operator and then try to meet the same production numbers. Would this be not adding muri? My understanding on this is that Ohno was very good at identifying all of the non-value adding activities in the process. He was able to see that the production can be run with fewer operators. He wanted to challenge the supervisor and the operators in kaizen by studying their standard work and improving their process.
I will finish off with a zen story about “mu” that I like a lot. This story is similar to this post in that it appears straightforward at first.
A monk asked Joshu, “Does a dog have the Buddha-nature or not?”
Joshu replied, “Mu.”
In this koan/story, Joshu is breaking the conventional thinking of the monk. In Mahayana Buddhism, the Buddha-nature is present in all beings including humans and dogs. The answer to the monk’s question should have been “yes”. But the monk’s perspective of nature of existence was one-sided and tunnel-visioned. Joshu challenged this and broke the monk’s mold of thinking by saying the answer “no”.
If Ohno was alive today and one were to ask him whether TPS was about eliminating waste, the master might have replied, “Mu”.
Always keep on learning…
In case you missed it, my last post was Respect for Humanity in the Light of Quality Control (QC).